Real-Time <tex>$4\times 3.5$</tex> Gbps Sigma Delta Radio-over-Fiber for a Low-Cost 5G C-RAN Downlink

Real-Time 100-GS/s Sigma-Delta All-Digital Radio-over- Fiber Transmitter for 22.75-27.5 GHz Band

“…SDoF simplifies RRHs by oversampling the signal and translating it to a bi-level signal, leveraging the benefits of both the DRoF (allowing low-cost telecom components) and ARoF (low-complexity RRH). Recently, we have verified the performance of this SDoF approach for sub-6 GHz systems by transmitting 4 parallel lanes of 3.5 Gb/s 256-QAM signals on a 3.5 GHz carrier over 20 km standard single-mode fiber (SSMF) at 1310 nm [4]. However, moving to higher frequency bands such as >24 GHz bands [5], SDoF has not been reported owing to the limited sampling rate of the state-of-the-art sigma delta modulators (SDMs) [6].…”

“…Cloud radio access networks (C-RANs) in combination with radio-overfiber (RoF) can be a key-enabling technology to realize this [2]. Three different realizations of the radio-over-fiber link, including digitized radio-over-fiber (DRoF), analog radio-over-fiber (ARoF) and sigma-delta-over-fiber (SDoF), have been discussed in our previous works [3,4]. SDoF simplifies RRHs by oversampling the signal and translating it to a bi-level signal, leveraging the benefits of both the DRoF (allowing low-cost telecom components) and ARoF (low-complexity RRH).…”

Real-Time 100-GS/s Sigma-Delta Modulator for All-Digital Radio-Over-Fiber Transmission

“…A centralized radio access network (C-RAN) in combination with radio-over-fiber (RoF) technology is viewed as one of the essential elements to address the challenges imposed by 5G [2]. Three different realizations of the radio-over-fiber link, including digitized radio-over-fiber (DRoF), analog radio-over-fiber (ARoF) and sigma-delta-overfiber (SDoF), have been thoroughly discussed in [3], [4]. SDoF features superior resilience against noise and nonlinear impairments from both optical and microwave components, and a simple structure with reduced latency at the remote radio unit (RRU).…”

“…The latter is beneficial to large-scale distributed antenna systems and ultra-dense networks such as the one proposed in [5]. In [3], we have verified the performance of this SDoF approach using low-cost off-the-shelf components by transmitting 4 parallel lanes of 3.5 Gb/s 256-QAM signals, processed by 7-GS/s sigma-delta modulators (SDMs) on a 3.5 GHz carrier and transported over 20 km standard single-mode fiber (SSMF) at 1310 nm. In [6], the authors demonstrated a real-time FPGAbased 5-GS/s sigma-delta modulator to digitize LTE signals with bandwidth up to 252 MHz and modulation scheme up to 1024-QAM at 960 MHz carrier frequency.…”

Analog Radio-Over-Fiber Transceivers Based on III–V-on-Silicon Photonics

“…At the antenna site only a bandpass filter is required to generate the RF signal. This approach was recently demonstrated in [1] for the transmission of 4x3.5Gbps 256-QAM signals on a 3.5 GHz carrier over 20 km of single mode fiber at 1310 nm and is a very attractive approach for sub-6 GHz, lower baudrate communication systems. Moving to the millimeter wave frequency bands (28 GHz and 60 GHz) and exploiting the wide bandwidth available in these frequency bands, will likely require moving to ARoF links, where a millimeter-wave signal, generated in the central office, is modulating an optical carrier.…”